Open vented system, No HW or CH, BAXI 80HE boiler shows Ignition Lockout after tried to start a few times

[fandyman]

Ok checked the flow and return at the boiler and they 62C and 53C correspondingly.

 

[Johntheo5]

Was that with HW&CH or just HW?

You said you would do the HW only test today with pump to CP2, if you do just monitor the boiler flow&return temps + pump power.

If the cylinder stat is set to 60C then the boiler will never cut out with a flow temperature of 62C, requires ~ 70C.

 

[fandyman]

That was HW&CH for now.

 

[Johntheo5]

So, with HW&CH on boiler output is, 13.3*60*9/860, 8.35kw, hardly enough to keep the boiler from cycling.

 

[fandyman]

I checked the HW only now and the pump shows 34W on CP2 while the temp readings on the boiler flow is 60C and return 50C.

 

[Johntheo5]

Same flowrate as with HW+CH, 0.8m3/hr, 13.33LPM, dT, 10C, blr output, 13.33*60*10/860, 9.3kw, just enough to keep the boiler constantly firing, will probably change depending on the cylinder temperature.

I don't think you can do much more now, bearing in mind the thread title was about ignition lockout which has gone away.

 

[fandyman]

What would be the long term solution? To have HW firing on demand?

I have this problem every spring to summer.

 

[Johntheo5]

Yes, your best bet is to fire the HW only, say a hour or so in the morning before the CH and something the same in the afternoon/evening.
In the summer, you require HW only so you could change to CC3 @ 6.4M but as the pump will be running at full power, 45W, you should get ~ 0.88/0.9m3/hr, say 14.6LPM, at 5.4M, which will squeeze a bit more out of the coil and keep the boiler running continuously for longer.
Of course increasing the boiler flow temp to max will give another boost and not cost a fortune in the summer with HW demand only.

 

[fandyman]

Thank you very much for your insights - it's been very valuable.

Yes, your best bet is to fire the HW only, say a hour or so in the morning before the CH and something the same in the afternoon/evening.

How do I achieve that as boiler shuts off after few minutes of HW only?

Of course increasing the boiler flow temp to max will give another boost and not cost a fortune in the summer with HW demand only.

Boiler flow temperature is already at max now.

Say a 10C dT, a bit unusual but the flow may be into the bottom (normal outlet) of the coil and out through the top (normal inlet), that gives a coil output of, 10*60*10/860, 6.98kw, (assuming flowrate @ 10LPM), fairly low, and may account for the boiler having difficulty in getting away and it will certainly cause the boiler to cycle sice the boiler's minimum output is > than the coil output.

The flow in top (normal inlet) and return is bottom (normal outlet)

Would you have any ideas as to why the temp measurements at the coil record such a drop? Is this normal?

Could it be the reason for the cylinder to not reaching stat temperature? Or could it be just air being trapped in the pipes hence frequent bleeding at the cylinder is required?

It still confuses me that after bleeding of the cylinder thumbvent the boiler does not fire up after few minutes.

In your opinion are the flow readings at the pump in CP2 and CC2 reasonable and not pointing to any issues?

Is it at all possible that the cylinder stat is causing issues telling the boiler the temp is reached even though it is only clicking at 50C when being raised to 60C?

Finally would you think that it could be the 3 port valve not directing the entire flow into the coil when in HW only?

I assume the pump is fully operational and no issues.

 

[Johntheo5]

Would you have any ideas as to why the temp measurements at the coil record such a drop? Is this normal? Could it be the reason for the cylinder to not reaching stat temperature? Or could it be just air being trapped in the pipes hence frequent bleeding at the cylinder is required? It still confuses me that after that bleeding the boiler does not fire up after few minutes. In your opinion are the flow readings at the pump in CP2 and CC2 reasonable and not pointing to any issues? Is it at all possible that the cylinder stat is causing issues telling the boiler the temp is reached even though it is only clicking at 50C when being raised to 60C? Finally would you think that it could be the 3 port valve not directing the entire flow into the coil when in HW only?
[/QUOTE]

A boiler max flow temp of your measured 60C seems very low, I don't have much faith in those infra red guns or whatever they are called.

I have no idea of the reason for the huge temperature differences, but would suggest you run the boiler continuously even if you have to use HW+CH, when the temperatures settle down take a set of readings, boiler flow/return temps, cylinder flow/return temps pump power, etc, then take a photo of the gas meter and exactly 2 minutes later (to the second) take another, X the difference X 11x60/2*0.88, to give the boiler output in kw, (assuming 88% boiler efficiency), can then compare this with the kw calculation using the boiler dT and the pump flowrate. Ensure the roomstat and cylinder stat are turned well up well up for these tests.

If the MPV is not directing all the water to the cylinder then pipe A (CH) will be hot all the way to the rads?.

You gave the coil flow/return temps originally with the outlet being the hotter I think??.